1. Field of the Invention
The present invention relates to an apparatus for driving a disk-type recording medium and more specifically, the apparatus which can be easily manufactured.
2. Description of the Related Art
A conventional floppy disk driving apparatus for driving a disk-type recording medium such as 3.5-inch floppy disk is arranged as shown in FIG. 1. That is, a spindle mechanism 111 and a carriage mechanism 112 as main portions are mounted on a frame 110 which constitutes an apparatus main body.
The frame 110 is generally made of an aluminum alloy diecast or a thick metal plate. The spindle mechanism 111 is for mounting and rotating a floppy disk and comprises a chucking unit 113 and a spindle motor 120 having a spindle shaft 114. The floppy disk is loaded in a receiver which vertically moves with an eject plate 115. In the receiver, the floppy disk is then chucked by the chucking unit 113 of the spindle mechanism 111 and rotated by the spindle motor 120.
The carriage mechanism 112 for moving the magnetic heads onto a destination track on the floppy disk includes an S0-side magnetic head 116 which is arranged at a lower end portion of a carriage of the carriage mechanism 112 to perform a read/write operation to a S0-side of the floppy disk and an S1-side magnetic head which is arranged to vertically face the S0 head 116 at a upper end portion of the carriage to perform the read/write operation to a S1-side of the floppy disk.
In this conventional apparatus, the spindle motor of the spindle mechanism 111 is fixed as an independent part on a circuit board 124 for the necessity of wiring, and the circuit board 124 is fixed on the frame 110. The carriage mechanism 112 is directly fixed on the frame 110. In a floppy disk driving apparatus, precision of a positional relationship from the magnetic heads to the spindle shaft 114 of the spindle motor is important. Since the motor is assembled as an independent part, however, workability is poor in order to obtain required precision.
In a conventional apparatus shown in FIG. 2, a spindle motor 120 of a spindle mechanism 111 includes a spindle shaft 114, a rotor 121 for transmitting rotation to the spindle shaft 114, a magnet 122 mounted under the rotor, a motor circuit board 124, and a stator coil 123 arranged on the motor circuit board 124. The spindle shaft 114 is supported by a bearing 126 fitted in a frame 110. The motor circuit board 124 is an insulating board consisting of, e.g., a glass epoxy resin and fixed on the frame 110 of a magnetic material steel plate in order to form a magnetic path.
The rotor 121 is rotated by an electromagnetic effect of the magnet 122 and the coil 123 to rotate the spindle shaft 114. As a result, a floppy disk 125 is rotated while it is chucked by a chucking unit 113. In this apparatus, since the motor 120 is formed integrally with the frame 110, the above problem of precision in positional relationship is more or less improved. However, since a glass epoxy insulating board is required as the motor circuit board, a manufacturing cost is increased. In addition, since the height of the apparatus is increased by the thickness of the circuit board, the apparatus becomes bulky.
In addition to the above apparatuses, a technique relating to the present invention is disclosed in Published Unexamined Japanese Utility Model Application No. 63-40852. This application describes that a rotating means and a chucking means are provided to a rotor. An apparatus in which a motor is mounted on a base plate consisting of a magnetic material and having an insulating layer is disclosed in Published Unexamined Japanese Patent Application No. 63-113879 or Published Unexamined Japanese Utility Model Application No. 61-58840. In these conventional apparatuses, however, a spindle shaft of a motor extends through the base plate. Especially in Published Unexampled Japanese Patent Application No. 63-113879, electronic parts are mounted only on the lower surface of the base plate. For this reason, a thin or compact apparatus cannot be obtained by these techniques.
The technique shown in FIG. 2 is described in Published Unexamined Japanese Patent Application No. 63-40865 and "Nikkei Mechanical", June 27, 1988. Published Unexamined Japanese Patent Application No. 63-40865 discloses a motor in which a turntable and a rotor boss are integrally molded and a rotor is mounted on the periphery of the integral unit. In this technique, however, a wiring circuit board is required in addition to a frame or a base plate. Similarly, in the technique described in "Nikkei Mechanical", a circuit board mounting electronic parts of a motor controller and other circuits is fixed on a frame.
That is, the conventional apparatuses for driving a disk-type recording medium has many problems to be solved in terms of, e.g., mounting precision, mounting workability, and the shape or size of an apparatus.